Saturday, July 20, 2013

Do you know the Datum of your Latitude and Longitude?

Last month I had the opportunity to present GeoFlow, now called Power Map, to the GIS team at my employer. Less than one minute into the live demo, I heard something like "That looks like a Mercator projection expecting a WGS84 Datum." Inside my head I was thinking "a what?"

I was not familiar with either map projections or datums. As datums are important when using latitude and longitude data, I'd like to share some of what I've learned about the topic since that presentation. The concept of datums can be quite large, so I'll just focus on what matters most to those of us using tools like Power Map and Power View. Those tools use Bing Maps for their geocoding. The primary point to make is that Bing Maps expects a WGS84 datum.

If your latitude and longitude coordinates do not correspond to the WGS84 datum, then your geographic points might not display in the proper location in Bing Maps. Let's first cover some basic points about datums.

Datum
  • Latitude and longitude always have a corresponding datum, such as WGS84 or NAD27
  • The latitude and longitude coordinates for your current position may vary across datums
  • Sometimes the difference may be less than a few hundred feet, but it may be much more drastic. WGS84 and NAD83 are nearly identical. The difference between NAD83 and NAD27 varies dependent upon your location within North America. If you're on the U.S. West Coast, the difference between NAD83 and NAD27 could be more than 300 feet. Further East the difference might be less than 100 feet
  • Map projections correspond to a datum
  • When gathering latitude / longitude data for geographic reporting, knowing the datum is important, as you may need to convert your coordinates to the proper datum before using them

Let's look at a basic example using lat/long coordinates for the Golden Gate Bridge.

Golden Gate Bridge Example

The following latitude and longitude coordinates are both valid for the Golden Gate Bridge:

37.819721, -122.478615 in WGS84
37.8197926, -122.4775316 in NAD27

Of the two, only the WGS84 coordinates will display on the Golden Gate Bridge in either Power Map or Power View.

The NAD27 coordinates do not display on the bridge


 The WGS84 coordinates properly display on the bridge



 Here's a comparison of the same coordinates in Power View


The above example provides a scenario where users are likely to notice the geographic point is not correct. That may cause them to not trust the data.

In some cases the difference may not be enough for users to notice. For example, I tried using NAD27 coordinates for several Smithsonian museums in Power Map. The tool displayed the column chart on the correct museum in most cases. The reason being that the museums are fairly large and the shift between WGS84 and NAD27 on the East Coast isn't as big as it is on the West Coast. There were a few Smithsonian locations, though, where the incorrect placement was noticeable.

Thus, when gathering and eventually using latitude and longitude coordinates for geographic reporting, it's important to make sure we know the corresponding datum.

For those interested in more advanced information on datums, you can find more information from Wikipedia here.

Wednesday, July 3, 2013

My Journey in the SQL Community / #SQLFamily

Last week two co-workers and I registered for our first PASS Summit!!! 

I've been heavily involved with the regional #sqlfamily for 3 years, but this is probably the first PASS event for either of my co-workers to attend. In order to prepare them for Summit I've been telling them about a few of my great #sqlfamily experiences. Talking to them got me thinking about my recent journey in becoming part of #sqlfamily and lead to this blog post.

SQL Saturday Dallas

In early 2010 I received an e-mail promoting a speakers call for an event I'd never heard of before. It was promoting a SQL Saturday, specifically SQL Saturday #35 in Dallas. Submitting to speak at that event, I believe was one of the best decisions of my professional career. Although speaking was a positive experience, the relationships I started building are what I both remember and value most. At the Speaker's Dinner and other portions of SQL Saturday Dallas, I met for the first time many of the following individuals: Sri Sridharan, Tim Mitchell, Ryan Adams, Sean McCown, Jen McCown, Bryan Smith (MS), Jeremy Marx, and many other great members of the SQL Community. Relationships quickly grew beyond the event. Within a few months Tim Mitchell was giving a remote presentation to OKCSQL speaking on "SSIS Scripting" and Bryan was presenting to OKCSQL in person. Contact with others from the SQL Community was continuing for various reasons, as well, including when Sri was asking for help with promoting Dallas’s bid to host SQL Rally.

My next SQL Saturday to attend was SQL Saturday #63 in Dallas in April 2011. As I was not actively presenting at the time, I chose not to submit to speak. Since I was a chapter leader, though, Sri still decided to invite me to the Speakers Dinner the night before the event. Side note, we had an OKCSQL officer speaking, as Rob Sullivan was a first time SQL Saturday presenter at that event. Multiple times during the Speakers Dinner, Rob and I heard, "When is Oklahoma City going to have their first SQL Saturday?" The answer was among the lines of "we'd need another OKC person to chair it, as Rob and I are the only two OKCSQL officers and don't have the capacity to take on running an event all by ourselves." Fast forward to the next day, someone introduced me to MattBrimer, also from Oklahoma. Matt Brimer was telling people that he wanted to help host a SQL Saturday Oklahoma City. 

SQL Saturday Oklahoma City 2011

Within a few months Matt was the newest OKCSQL officer and Event Chair for SQL Saturday #90 in Oklahoma City, with me as Speaker Chair, and a Rob Sullivan, Jamin Mace, and Amanda Hardeman (now Harlin) also on the Event Committee. Relationships with Texas members of the #sqlfamily were absolutely critical to us being able to host a well-run 200 person event. When asked, Sri provided us his sources for anything from event insurance to event bags. Texas speakers, several MVPs, comprised 11/14 of our first event’s speakers. The night before the event, Ryan Adams and others were giving us advice and double-checking that we’d covered certain things. I remember the advice being great, and at least one item was changed last minute due to the conversations. The event itself took place on August 27th, 2011, less than 5 months after we had met Matt. The event was high energy with a lot of great sessions, and we got some really good feedback.

SQL Rally 

The following year SQL Rally 2012 took place in Dallas in May. My involvement started before the event, as I volunteered to assist with session selection. That was a great opportunity to be involved with some “behind the scenes” for an international event and gave me some great ideas for how to handle session selection for our next SQL Saturday Oklahoma City. I personally paid for all my SQL Rally expenses, and it was definitely worth attending! While at SQL Rally, I got to hear some great presentations by some people I’d never seen in person before like Adam Jorgensen, Devin Knight, Jen Stirrup, Vicky Harp, and Julie Koesmarno (@mssqlgirl). Although, I didn’t meet all of them in person, I remember a great long conversation that a couple of us had with Adam Jorgensen and later with Rob Farley. Lately I've been learning a lot from the the BI blogs of several of the speakers from SQL Rally.

SQL Saturday Oklahoma City 2012

SQL Saturday #125 in Oklahoma City took place in August 2012, with a lot of great speakers returning and some talented new ones coming in. As we were getting close to the event, I remembered thinking "I can't wait to see Sean, Jen, Tim, Ryan, Mike, and the names rolled on." I also met Grant Fritchey, Carlos Bossy and others for the first time. The relationship building continued. On the relationships note, when 2 of the SQL Saturday OKC 2011 speakers didn’t make the 2012 cut due to the 90+ submissions we had for 24 sessions, I made sure that they were each invited to the Influencers’ Dinner. We started using that name, since we include Sponsors, event committee, speakers, former speakers, chapter leaders, and more. Relationships are critical, and we don’t want to exclude someone passionate about SQL because they happened to not have time to commit to prepping a session or didn’t get selected to speak.

This past Monday evening I was on a Google+ Hangout with TulsaSQL President Jeremy Marx. He’s the Speaker Chair, under my mentorship, this year for SQL Saturday #223 in Oklahoma City to take place on Saturday, August 24th. We were talking about final session selections for the event. I can’t believe it’s almost time for Oklahoma City’s 3rd SQL Saturday.  It was just over two years ago that I met Matt Brimer, and around three years ago that I attended my first SQL Saturday. Several people that I met at Dallas’s first SQL Saturday will be speaking at their 3rd SQL Saturday Oklahoma City. Their continued support has been amazing.

Although, my #sqlfamly involvement started to sky-rocket with my attendance at SQL Saturday Dallas, there are some key relationships I made before then. I met Greg Galloway at the Microsoft BI Conference in 2007. We had some e-mail conversations where he helped me out with some SSAS processing strategies. I was quite the SSAS newbie at the time! We lost contact at some point, but then through his connection to Tim Mitchell, Greg ended up speaking at Oklahoma City’s first SQL Saturday.  I met Mike Hotek in 2009 when he was consulting at my then employer. Mike helped OKCSQL start strong by being our speaker for the first 3 OKCSQL meetings, which were averaging around 25 attendees. That was just our first great experience with Mike and his SQL Community involvement. Of course, I can’t forget Rob Sullivan with whom I co-founded OKCSQL back in April 2009. I met Rob a couple of years earlier in the Oklahoma City .Net Developers Group. In 2008 he was Sr. Vice President during my one year term as President of the OKC.Net group.

As I type this blog post, I keep thinking of so many more people I’ve met just in the past 3 years like BillPearson, Tim Costello, and our newest OKCSQL officer Allen Smith. There are too many to mention in one blog post.

I also keep thinking back to SQL Rally 2012, when Sri was passing out #sqlfamily stickers. This is a great family to be a part of and I can’t wait to build even more relationships and help others join this great #sqlfamily.

Below are some of my favorite #sqlfamily photos.

SQL Saturday Oklahoma City 2011

Most of the TX speakers and crew. Top row: Sri Sridharan, Ryan Adams, Shawn Weisfeld, Russel Loski, and Paul Hunter. Bottom row: Tim Mitchell, Greg Galloway, Jen McCown, and Sean McCown.

Speaker Paul Hunter with Rob Sullivan (event committee)

 Jeff Blankenbiller (my husband) and Sean McCown (Jen's husband)

 Matt Brimer and I on stage together

Event Committee on stage together (Matt's wife, Matt Brimer, Jamin Mace, Rob Sullivan, Amanda Hardeman, and I)

SQL Rally 2012


 With Julie Koesmarno (@mssqlgirl on the right) after her awesome session! I've been reading her blog lately to learn more about GeoFlow. I've been selected to speak on that topic at SQL Saturday Oklahoma City 2013

@VickyHarp rocking it with Karaoke at a SQL Rally 2012 Party
 
Future OKCSQL Officer Allen Smith on stage as a volunteer with presenters Adam Jorgensen and Devin Knight

SQL Saturday Oklahoma City 2012


Grant Fritchey and Jen McCown



Grant Fritchey, Tim Mitchell, Ryan Adams, Carlos Bossy, and Jeff Blankenbiller hanging out the night before

More photos from SQL Saturday Oklahoma City 2011 available at
http://www.flickr.com/photos/timdmitchell/sets/72157627532203718/ thanks to Tim Mitchell.